The present disclosure relates generally to fluid actuators on vehicles and machinery. The terms vehicle and machinery, herein, include, among other things, rail locomotives and rail cars, as well as agricultural and logging vehicles, machinery and implements
The prior art, for example, discloses fluid actuators on parking brakes for rail vehicles. Some parking brakes operate independently of the overall brake system for the train and others are integrated with the overall brake system, particularly by using the main brake cylinder that operates the train's brakes. Some parking brakes have cylinders or actuators that lock a parking brake in an applied position.
In general, the main brake system for rail vehicles is pneumatically operated. The brake system includes a brake cylinder with a piston rod to operate the brake shoes to engage the wheels and brake the rail vehicle. The brake cylinder receives a signal to apply the brakes and generally has a spring return to release them. The signal or force to activate the brakes is generally multiplied by some sort of lever that is located between the brake cylinder and the brake shoes.
Most rail vehicles have a manually-operated parking brake that applies the wheel brakes. Generally, for truck-mounted brake systems, which are well-known in the art, one end of the brake cylinder has a piston rod output that is connected to levers or similar elements which connect the brake cylinder to the brake beams. Furthermore, as part of the parking brake system, a combination of chains, levers, hoses, rods and cables are generally used to connect a manual-hydraulically operated actuating device to the brake cylinder. The actuating device may be located at any convenient place on the rail vehicle to allow remote operation of the parking brake.
The prior art also discloses an electropneumatic controlled parking brake, that is one that has electrical and pneumatic elements.
Manual fluid pumps to actuate separate hydraulic parking brakes on railroad vehicles are also disclosed in the prior art. Those parking brakes are connected to the brake beams and may or may not be independent of, or not connected to, the main brake cylinder.
Locking mechanisms in actuators for parking brakes are also known from the prior art. Those locking mechanisms, which generally lock a parking brake in an applied position, are constructed in a variety of ways. For example, there are mechanisms that use detents for locking a parking brake and there are mechanisms that use concentric clutch surfaces or opposing clutch surfaces to lock a parking brake. A known locking mechanism for a parking brake includes a rotating nut and a slidable sleeve that are external to an actuator piston. The known parking brake has a piston shaft that is connected to the rail vehicle's brakes and a connecting rod attached to a brake cylinder that applies and releases the brakes. The shaft and rod move linearly together, thereby requiring a certain amount of space for a given piston stroke for the operation of the parking brake.
An aspect of the present disclosure relates to an actuator for a parking brake that takes up less space on a rail vehicle compared to known actuators, particularly in relation to a given piston stroke, for example, of known actuators.